Gelsolin and progression of aortic arch calcification in chronic hemodialysis patients

Vascular calcification (VC) is a key process associated with cardiovascular mortality in dialysis patients. Gelsolin is an actin-binding protein that can modulate inflammation, correlated inversely with hemodialysis (HD) mortality and involved in bone calcification homeostasis. In this report, we aim to characterize progression in aortic arch calcification (AAC) and investigate its association with gelsolin.

Int J Med Sci 2016, Vol 13 Ivyspring International Publisher 92 International Journal of Medical Sciences 2016; 13(2): 92-98 doi: 10.7150/ijms.13785 Research Paper Gelsolin and Progression of Aortic Arch Calcification in Chronic Hemodialysis Patients Terry Ting-Yu Chiou1, Shang-Chih Liao1, Yu-Yin Kao1, Wen-Chin Lee1, Yueh-Ting Lee1, Hwee-Yeong Ng1, Po-Shun Lee2, Chien-Te Lee1 Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang-Gung University College of Medicine, Taiwan Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA  Corresponding author: Chien-Te Lee M.D., Ph.D Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang-Gung Memorial Hospital, Taiwan 123 Ta-Pei Road, Niao Sung District, Kaohsiung 833, Taiwan TEL: 886-7-7317123 EXT 8306 FAX: 886-7-7322402 E-mail: chientel@gmail.com © Ivyspring International Publisher Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited See http://ivyspring.com/terms for terms and conditions Received: 2015.09.07; Accepted: 2016.01.05; Published: 2016.01.29 Abstract Background: Vascular calcification (VC) is a key process associated with cardiovascular mortality in dialysis patients Gelsolin is an actin-binding protein that can modulate inflammation, correlated inversely with hemodialysis (HD) mortality and involved in bone calcification homeostasis In this report, we aim to characterize progression in aortic arch calcification (AAC) and investigate its association with gelsolin Methods: 184 HD patients were enrolled and their annual posterior-anterior chest X-ray films (CXR) in 2009 and 2013 were examined The severity of AAC was classified as grade to Blood levels of gelsolin were measured by ELISA kits Biographic and biochemical data at baseline were analyzed with status of AAC at baseline and changes after years Results: At baseline, 60% of the patients had detectable AAC on CXR After years, 77% had AAC Patients with grade and AAC had increased risk of progression (Odds ratio [OR] 2~3, P=0.001) compared to those with grade at baseline Compared to those with no AAC, patients with AAC progression had older age, lower gelsolin, higher waist circumference and prevalence of vascular disease Regression analysis confirmed baseline gelsolin (odds ratio 0.845, 95% confidence interval [0.734-0.974]) and waist circumference as the independent factors associated with AAC progression Gelsolin is positively correlated with serum albumin and negatively with tumor necrosis factor-alpha Conclusion: Our study demonstrated that HD patients with grades or baseline AAC are at increased risk of further progression compared to those with grade We also found lower blood levels of gelsolin associated with progressive AAC Further investigation into the mechanistic roles of gelsolin in vascular calcification may provide new understanding of this key process Key words: Aortic arch calcification, gelsolin, hemodialysis Introduction Cardiovascular disease is the most common cause of death in patients on chronic dialysis [1] Vascular calcification (VC) is increasingly recognized as a key process contributing to the high cardiovascular mortality in dialysis patients [2-4] Our previous study on 712 prevalent hemodialysis (HD) patients showed a strong correlation between aortic arch calcification (AAC) and 10-year mortality [5] It also substantiated the use of plain chest X-ray films (CXR) as a simple tool to evaluate AAC Recent studies reported that 26~78% of dialysis patients had various degrees of AAC on CXR, and 34~60% had progression after 1~5 years of follow-up [6-10] These variations in the prevalence of calcification and its progression may be related to the differences in ethnicity, comorbidity, length of observation, http://www.medsci.org Int J Med Sci 2016, Vol 13 and methods of assessment Progression in VC has also been associated with mortality [6,7] Factors contributing to VC include age, comorbidity (diabetes, hypertension, metabolic syndrome, dyslipidemia), dialysis vintage, medications (calcium, vitamin D, coumadin), and uremia-related mineral bone disorder (serum calcium [Ca], phosphorus [P], parathyroid hormone [PTH]) [11-15] Markers of inflammation and oxidative stress have also been implicated [16,17] Gelsolin, by regulating intracellular actin filaments, is important in cell morphology, migration and phagocytosis [18] Its extracellular isoform, plasma gelsolin is secreted by different types of cells and serves as a scavenging system for potentially toxic actin filaments [19] It can localize inflammation and minimize tissue damage by binding excessive actins released from tissue injury The phenomenon of plasma gelsolin depletion has been observed in different diseases Specifically, in patients with acute myocardial infarction and fulminant hepatic failure, plasma gelsolin levels dropped dramatically and recovered if organ function improved from injury [20] Further research found that in addition to actin, plasma gelsolin may also modulate immune response by binding to key inflammatory mediators, including lipopolysaccharide, lysophospholipids, and platelet activating factor [21,22] Furthermore, gelsolin interacts with osteopontin and both are involved in bone homeostasis [23] In HD patients, plasma gelsolin levels were reduced nearly 50% compared to healthy volunteers and correlated with mortality and protein-energy wasting [24,25] However, whether gelsolin have independent roles in vascular calcification is uncertain, and strategies to reduce inflammation and protect vascular integrity are poorly defined In this report, we aim to characterize the progression of aortic arch calcification in HD patients and investigate its associations with novel biomarker gelsolin Subjects and Methods From January to December 2009, we enrolled 184 stable HD patients from Kaohsiung Chang Gung Memorial Hospital Inclusion criteria were over 20 years of age and regular 4-hour HD session three times a week for at least months Exclusion criteria were chronic viral hepatitis, malignancy (within years), acute infection or hospitalization (within three months) This study was approved by the Institutional Review Boards and Ethics Committee in Chang Gung Memorial Hospital (IRB No 98-2685B), and informed consents were obtained from all participants 93 Laboratory and Clinical Data For every study participant, blood samples were collected The averages of biochemical data were obtained over the three months prior to study enrollment The adequacy of dialysis was assessed by Kt/V urea using the urea kinetic model of Gotch [26] Gelsolin levels in blood were measured with ELISA kits from Critical Biologics Corporation (Cambridge, MA USA) The immunoassay kits for interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were from R&D Systems, Minneapolis, MN USA All measurements were done in duplicate All patients’ medical records were carefully reviewed Vascular disease was identified by documented history of ischemic heart disease, cerebrovascular disease or peripheral vascular disease Evaluation of AAC on Chest Radiography Our HD patients have chest X-ray examinations (posterior-anterior approach, standing) annually For each study participant, the routine annual chest X-ray film in 2009 was selected as the baseline A second follow-up chest X-ray film was selected in 2013 or the year when the patient reached outcomes such as death, kidney transplantation or transfer to other dialysis centers A simple classification by Symeonidis et al [27] was used to evaluate AAC in the present study Briefly, the severity of calcification was classified as grade (Gr.) (no calcification visible), Gr (single thin or small spots of calcification), Gr (one or more areas of thick calcification, but ≤ 50% of the circular area of the aortic knob) and Gr (circular calcification with >50% of circular area of the aortic knob) Each posterior-anterior (P-A) chest X-ray (CXR) of these HD patients was read and graded independently by two readers (one nephrologist and one trained nurse practitioner) blinded to the patients’ clinical data Eight X-rays were graded differently on calcification score (±1) The discrepancies between the two observers were resolved by a third independent reader The progression of aortic calcification was determined by comparing the grades at baseline and at follow-up “Progressive AAC” was defined if the second chest X-ray’s grade is greater than the first one “Stable AAC” was defined if the first CXR showed calcification and the second CXR had the same calcification grade “No AAC” group was defined if both the first and second CXR’s were grade Statistical Analysis Statistical analysis was performed using SPSS version 12.0 Results were expressed as mean ± standard deviation or median (interquartile range) for nonparametric data Comparisons between two http://www.medsci.org Int J Med Sci 2016, Vol 13 groups were performed using Student t-test or Mann-Whitney test for nonparametric data We used multiple logistic regressions to examine the independent relationships between AAC progression (progressive vs no AAC) and other variables Regression adjusted for age, HD vintage, vascular disease, BMI, waist circumference, Kt/V, parameters of mineral-bone disorder (serum calcium [Ca], phosphorus [P] and intact parathyroid hormone [iPTH]), gelsolin and IL-6 All results were considered significant if P-value was less than 0.05 Results Aortic arch calcification and its progression At baseline, the subjects with and without AAC had similar dialysis adequacy (Kt/V 1.38 ± 0.22 vs 1.45 ± 0.23, P>0.05) and biochemical control, particularly serum calcium (9.2 ± 0.8 vs 9.4 ± 0.9 mg/dL, P>0.05) and phosphate (4.8 ± 1.4 vs 4.9 ± 1.4 mg/dL, P>0.05) 75 (40%) patients had no detectable AAC (grade 0) on plain chest X-ray 52 (28%) patients had grade 1, 43 (23%) grade 2, and 14 (8%) grade (Figure 1A) Figure Distribution of different grades of aortic arch calcification (AAC) at (A) baseline and (B) after years of follow-up After years of follow-up, only 43 (23%) patients remained at grade Thirty-one (17%) patients had grade 1, 46 (25%) grade 2, and 64 (35%) grade (Figure 1B) Moreover, 32 (43%) of those with grade at baseline progressed to higher grades of AAC over years 73% (38/52) of those with grade at baseline had progressive AAC, and 84% (36/43) of those with grade at baseline had progressive AAC Fourteen patients with grade calcification at baseline re- 94 mained so after years Compared to those with grade (the reference group), patients with grade at baseline had increased risk of further progression in AAC (Odds ratio [OR] 2.11, 95% confidence interval [CI] 1.29-3.44, P=0.001, adjusted for age, waist circumference, gelsolin and IL-6) Patients with grade at baseline also had higher risk of progression in AAC (OR 3.49 [1.72-7.07], P